1. Field of the Invention
The present invention relates generally to wafer processing processes and to equipment for processing wafers, and more particularly to methods and apparatus for correlating gap value to meniscus stability in processing of a surface of a wafer by a recipe-controlled meniscus.
2. Description of the Related Art
In the semiconductor chip fabrication industry, it is necessary to clean and dry a wafer (e.g., a substrate) after a fabrication operation if, e.g., the operation leaves unwanted residues on surfaces of the substrate. Examples of such a fabrication operations include plasma etching and chemical mechanical polishing (CMP), each of which may leave unwanted residues on surfaces of the substrate. Unfortunately, if left on the substrate, the unwanted residues may cause defects in devices made from the substrate, in some cases rendering the devices inoperable.
Cleaning the substrate after a fabrication operation is intended to remove the unwanted residues. After a substrate has been wet cleaned, the substrate must be dried effectively to prevent water or other processing fluid (hereinafter “fluid”) remnants from also leaving unwanted residues on the substrate. If the fluid on the substrate surface is allowed to evaporate, as usually happens when droplets form, residues or contaminants previously dissolved in the fluid will remain on the substrate surface after evaporation and can form spots. To prevent evaporation from taking place, the cleaning fluid must be removed as quickly as possible without the formation of droplets on the substrate surface. In an attempt to accomplish this, one of several different drying techniques may be employed such as spin-drying, IPA, or Marangoni drying. All of these drying techniques utilize some form of a moving liquid/gas interface on a substrate surface, which, only if properly maintained, results in drying of a substrate surface without the formation of droplets. Unfortunately, if the moving liquid/gas interface breaks down, as often happens with all of the aforementioned drying methods, droplets form, droplet evaporation occurs, and contaminants remain on the substrate surface.
In view of the foregoing, there is a need for improved cleaning systems and methods that provide efficient substrate cleaning while reducing the likelihood of contaminants remaining on the substrate surface from dried fluid droplets.